Intriguing! The spell list can indeed get very, very long and such a feature is welcome. Perhaps only, this filtering method is rather command-line-like, and filtering by other methods, by spell effect or similar, would be more game-convenient-like?

You might want to take some inspiration from how SKSE does things. I'm pretty sure they have a column in the spell list for effect type and clicking the heading of that column sorts alphabetically by effect type.